Peristaltic pump



Jan. 30, 1968 H. DUTLER PERISTALTIC PUMP Filed July 29, 1966 Fig. 2

United States Patent f 3,366,071 PERISTALTIC PUMP Hans Dutler, Zurich, Switzerland, assignor to LKB- Produkter AB, Stockholm-Bromma, Sweden, a firm of Sweden Filed July 29, 1966, Ser. No. 568,917 Claims priority, application Switzerland, Aug. 3, 1965, 10,911/ 65 Claims. (Cl. 103-149) ABSTRACT OF THE DISCLOSURE The peristaltic or tube squeezing pump is of the planetary type, i.e. it has rollers without individual bearings and contacting a central driving member which preferably is circular. The rollers are arranged to roll on the tube and on a rolling face along different portions of their travel. In each roller the portion contacting the tube has a slightly greater diameter than the portion contacting the rolling face so that a slight recoil movement of the said tube contacting portion is produced while the roller is rolling on the rolling face.

This invention relates to improvements in peristaltic pumps of the kind having a tube carried by a supporting face and rollers movable along the tube for compressing it.

In known peristaltic or tube squeezing pumps of this kind each individual roller is rotatably mounted on a carrier and the carrier, for example a rotatable carrying member or a pair of rotating chains, is in its turn movably mounted. In such pumps therefore there is a plurality of stressed bearings which have to be lubricated and are subjected to wear.

In order to obviate these drawbacks the peristaltic pump of this invention is characterized in that the rollers are held capable of being rolled freely on the tube and/or a rolling face without central bearing of each roller and are capable of being driven by means of a common driving member by frictional engagement on a place lying diametrically opposite the place of contact with the tube.

The construction of this pump may therefore be compared to that of a roller bearing with a driven inner ring, the tube being located between the roller bodies and the stationary outer ring.

A further drawback of the known peristaltic pumps is that the tube under the action of the roller rolling on it has a tendency to wander. Consequently the tube, firmly held in the pump, is periodically stretched and released again whereby a heavy stressing and premature instability of the tube result.

This phenomenon may be obviated in the pump according to the invention by forming the rollers with two parts of slightly different diameters and allowing the part of smaller diameter to roll on a rolling face whilst the part of greater diameter presses on the tube whereby the contact place carries out a recoil movement.

One embodiment of the peristaltic pump according to the invention is illustrated in the drawing in which:

FIGURE 1 shows a plan view of the pump with the cover plate removed and FIGURE 2 shows an axial section of the pump.

The pump illustrated has a casing with a dish-shaped lower part 1, for example of polyvinyl chloride, and a cover plate 2 detachably fixed by means, not shown, to the lower part 1. The cover plate 2 is for example made of Plexiglas. In this casing six rollers 3 of synthetic material, for example of Delrin (registered trade mark) are arranged so that their axes lay on a circle. The rollers 3 each have an upper flange portion 3a, the periphery of 3,366,071 Patented Jan. 30, 1968 which rolls on a portion of an elastic tube 4 bent approximately circularly in order to squeeze the same and to cause a medium located in the tube 4 to move through the tube in the direction of movement of the rollers 3. The tube 4 is supported by a supporting face 5 of the casing 1. A lower part 3b of each roller 3 is recessed to provide a traction portion which rolls on a cylinder-likerolling track or face 6 in the lower part 1 of the casing.

The tube supporting face 5 embraces three adjacent sections 5a, 5b and 5c each extending over an angle of 60. The middle section 5b lies on a cylinder coaxial with the rolling face 6 whilst the two outer sections 5a and 5c lie on a cylinder with the axis A (FIGURE 1) arranged eccentrically of the rolling face 6.

The radius of the section 5b is so selected that the section of tube lying on this section 512 is completely compressed by the roller 3 in question, that is, such that the inner space of the tube is closed.

The eccentricity of the sections 5a and 5c of the supporting face 5 is so dimensioned that the tube 4 in these sections is compressed gradually from the full free diameter of the tube and released from complete closing, respectively. At the beginning of the section 5a and at the end of the section 5c the distance between the periphery of the roller 3 and the supporting face 5 is therefore equal to the outer diameter of the non-deformed tube 4 whilst in the whole of section 5b this distance is equal to about twice the wall thickness of the tube. This arrange ment with six rollers 3 and the three sections 5a, 5b and 5c each extending over 60 ensures a shock-free movement of the fluid in the tube 4 in the direction of movement of the rollers. It will be clear that because of the symmetrical construction of the pump the rollers 3 can be moved in both directions of rotation, the pump can therefore work selectively in both directions.

For taking the counter pressure exercised by the tube 4 on the rollers 3 a pressure ring 7 is disposed between the upper parts 3a of the rollers.

The rollers 3 are driven by a wheel 8 which is in contact with the lower parts 3b of the rollers via an O-ring 8a of rubber and a driving ring 9 placed over this O-ring.

The pressure ring 7 and the driving ring 9, for avoiding deformation and wear, should not consist of a material which is too soft. They should however be somewhat resilient in the peripheral direction in order to compensate tolerances. The rings 7 and 9 therefore consist preferably of a relatively hard synthetic material such as, for example, of Delrin and they are provided with radial slots 7a and 9a, respectively, which extend alternately from the top and from the bottom over a little more than half the height of the rings.

The wheel 8 is in its turn driven by a coupling piece 12 centered in the wheel 8 by means of a further O-ring 11 and fixed on a driving shaft 10 which coupling piece engages with two pins 13 in corresponding slots 14 in the wheel 8. It will be clear that the driving shaft 10 does not have to take up any radial or axial forces and that no accurate alignment of this shaft is necessary.

As can be seen from the drawing the upper parts 3a of the rollers 3 have a somewhat larger diameter than the lower parts 3b. This results in that, in the sections 5a and 5c in which the lower roller parts 3b roll on the rolling face 6, the contact places of the upper roller parts 3a with the tube carry out a slight recoil movement which counteracts the tendency to wander of the tube which occurs in the known peristaltic pumps.

In the section 5b in which the tube 4 is completely compressed in line by each roller 3 the said recoil movement is not desired because it would lead to too great a stressing of the tube. The radius of the section 5b of the supporting face 5 and the outer radius of the pressure ring 7 are therefore so adapted to one another that in the section b each roller 3 is raised quite a little from the rolling face 6 and rolls on the tube 4. It is clear that a roller when located in the section 5b is thereby moved a little more quickly than the remaining rollers, therefore, the rollers 3 must at least at this place have a small clearance (FlGURE 1). In order to compensate for any differences in the dimensions of the tube, it may also be advantageous to provide below the supporting surface section 5b in the rolling face 6 a recess (not shown) which extends preferably from the upper edge of the rolling face beyond about "-X; of the width thereof. In such case the roller 3 rolls in the section 512 only on the lower third of the rolling face 6 and at the same time with the part 3a on the tube 4 whereby the roller can carry out if necessary a slight tilting movement.

The rollers 3 (and the pressure ring 7) are held between the base of the under part of the casing 1 and the cover plate 2. A sliding friction takes place on the places of contact. Although this friction does not take place under pressure it may be advantageous to cover the base of the under part 1 of the casing and the underside of the cover plate 2 with exchangeable discs and 16, respectively, for example of Celluloid.

At all other parts of the pump and in particular at the pressure transmitting parts there does not take place any relative sliding movement but only a rolling friction so that lubrication is not necessary and practically no wear takes place. For the driving of the pump a minimum power is suflicient which, for example, can be produced from a small synchromotor with reduction gear.

lthough wear and tear and wearing away of material in the pump described are very slight it may be advantageous to provide at suitable places small incisions or notches which can take up any particles removed by abrasion so that they do not fall between the faces rolling on one another and attack same. Such incisions or notches (not shown) may for example be provided in the upper side and lower side of the rollers 3 and possibly in the lowermost part of the peripheral surface of the roller part 312 as well as also in the lower side of the lower flange of the wheel 8.

The pump described is very simply constructed and cheaply manufactured; it may if necessary be taken to pieces easily for cleaning purposes for which only the cover plate 2 has to be removed, and all individual parts are exchangeable without trouble.

With suitable dimensioning of the pressure ring 7 it is possible as mentioned in the foregoing description to produce in the sections 5a and 5c a recoil movement of the contact places between the tube 4 and the rollers 3, counteracting a tendency to wander of the tube, whilst in the section 5b the counter pressure of the completely compressed tube suflices to take care that the roller 3 in this section rolls on the tube and no longer on the rolling face 6. The tube 4 is thereby compressed no more than is necessary for its complete closing. There thus results a protective pressing of the tube so that it has a relatively long life even if it consists of sterilizable and chemically resistant silicone rubber.

Various alterations in the construction of the pump are possible without departing from the invention. Thus, for example, several tubes arranged over one another can be compressed together by means of the rollers 3. The tubes may be supported on supporting faces arranged separately symmetrically above and below the rolling face 6 whereby the rollers would each have two heads 3a. In a similar manner it is possible to assemble several pumps as before described to form a unit driven from a common shaft.

There need not necessarily be six rollers 3 provided. If with another number of rollers the described uniform, impact free output is desired only the length of the sections 5a, 5b and 5c need be varied, i.e., adapted to the distance between adjacent rollers.

Furthermore the rollers need not be arranged on a circle. Their arrangement, for example, in an oval is feasible; the wheel 8 in this case must be replaced by a driving member, for example, in the form of an endless band of suitable shape contacting the rollers.

What I claim is:

1. A peristaltic pump comprising a collapsible tube (4), a supporting face (5) for said tube, a rolling track (6), said rolling track defining a closed path and being adjacent to said supporting face (5) over a part of said path, a plurality of rollers (3), each of said rollers having an annular flange (3a) and a reduced diameter traction portion (3b), a common driving member (8) for rolling said rollers over said closed path so that said flanges engage said tube (4) and said traction portions engage said track (6), the distance between said rolling track (6) and said supporting face (5) varying along said part of said path so that at a location where said distance is comparatively small said tube (4) is compressed between said flanges (3a) and said supporting face (5) and at a location where said distance is comparatively large said flanges do not collapse said tube but maintain frictional engagement therewith to urge said tube in a direction opposite to the general direction in which said rollers are rolling.

2. The peristaltic pump defined in claim 1 wherein said part of said path comprises a first section in which each of said rollers (3) enters with said traction portion (311) in rolling contact with said track (6) and wherein said distance between said track and said supporting face becomes less as said roller travels through said first section so that said tube is gradually compressed between said flange and said supporting face until said tube is completely collapsed, a second section wherein said distance between said supporting face and said track is constant over the length of said second section and sufliciently small so that said flanges (3a) completely collapse said tube (4) as they travel over said second section, and a third section wherein the distance between said supporting face and said track gradually increases over the length of said section so that as each of said rollers travels said third section said tube gradually opens.

3. The peristaltic pump defined in claim 2, wherein said rollers (3) are positioned substantially equidistant along said tube and the length of each of said sections is approximately equal to the distance between the locations on said tube contacted by said flanges.

4. A peristaltic pump comprising a curved supporting face (5), a flexible tube (4) positioned on said supporting face, a generally circular roiling track (6), a part of said rolling track (6) being adjacent to said supporting face (5), a plurality of planetary rollers (3), each of said rollers having an annular flange (3a) for rolling over said tube and an axially spaced reduced diameter track portion for engagement with said track, a driving wheel disposed between and adapted to drive said rollers, the distance between said rolling track (6) and said supporting face (5) varying along said part of said rolling track so that, at a location where said distance is comparatively small, said tube is completely collapsed between said flanges and said supporting face, and at a location where said distance is comparatively large said tube is not completely collapsed between said flanges and said supporting face and said traction ortions roll on said rolling track while said flanges spin on said tube to urge said tube in a direction opposite to the general direction in which said rollers are driven by said driving wheel.

5. The peristaltic pump defined in claim 4, further comprising a rubber ring (8a), said ring being disposed about the periphery of said driving wheel (8), a hard driving ring (9), said driving ring being disposed about the periphery of said rubber ring, a plurality of slots (9a) extending radially over the top and bottom of said driving ring (9).

6. The peristaltic pump defined in claim 4, wherein said supporting face (5) comprises three sections adjoining one another, the middle one (5b) of said sections being coaxial with said rolling track (6), the other two of said sections being on either side of said middle section and each being in the form of a cylindrical section eccentric with respect to said rolling track, the radii of said rolling track and said three sections being so chosen that in the section (5a) first traversed by said rollers said flanges (3a) gradually compress said tube (4), until it is closed, in said middle section (5b) said rollers roll with said flanges on said tube to maintain said compression and in the third section (5c) said rollers roll with said traction portion on said rolling track and gradually release said compression.

7. The peristaltic pump defined in claim 6, wherein said rolling track is partially recessed along a portion thereof adjacent to said middle section of said supporting face so that said rollers contact both said tube and a non-recessed portion of said rolling track.

8. The peristaltic pump defined in claim 6, wherein said rollers (3) are six in number and are substantially uniformly distributed on a circle having a diameter such that said rollers are only at a slight distance from one another and wherein said three sections of said supporting face each extend over an angle of at least approximately 60.

9. A peristaltic pumpcomprising a curved supporting face (5), a flexible tube (4) positioned on said supporting face, a generally circular rolling track (6), a part of said rolling track being adjacent to said supporting face, a plurality of planetary rollers (3), each of said rollers having an annular flange (3a) for rolling over said tube and an axially spaced reduced diameter track portion (3b) for rolling on said track, a driving wheel (8) disposed between and adapted to drive said rollers, said driving wheel being axially aligned with said traction portion of each of said rollers, the distance between said rolling track and said supporting face varying along said part of said rolling track, so that, at a location where said distance is comparatively small, said tube is completely collapsed between said flanges and said supporting face and, at a location where said distance is comparatively large, said tube is not completely collapsed between said flanges and said supporting face, said traction portions being adapted to roll on said rolling track and said flanges to spin on said tube to urge said tube in a direction opposite to the general direction in which said rollers are being driven by said driving wheel, and a pressure ring disposed between said rollers and axially aligned and in contact with each of said flanges.

10. The peristaltic pump defined in claim 9, further comprising a plurality of radial slots on the top of said pressure ring and a plurality of radial slots on the bottom of said pressure ring.

References Cited UNITED STATES PATENTS 819,690 5/1906 Bryson 103149 2,899,904 8/1959 Becher 103149 2,899,906 8/1959 Becher et a1. 103149 3,249,059 5/1966 Renn 103-149 ROBERT A. OLEARY, Primary Examiner. WILBUR I. GOODLIN, Examiner. 

